Principle of operation 

The RST Magnetic Settlement System – Reed Switch Probe is a simple, reliable system designed to monitor settlement or heave in rock, soil and different types of manmade structures. The system consists of an access pipe, target magnets, probe and readout unit.  

The Reed Switch Probe employs a high accuracy, NBS traceable or polyethylene coated, non-stretch, flat tape that is permanently marked in 1/100ft. and/or 1mm graduations. Ring magnets elevation can be read from the tape. The moisture resistant electronics and a standard 9-volt battery are also housed in the reel hub. 

Both the tape and the probe are supplied on a sturdy winding reel with a braking system.  The brake is applied by tightening the thumbscrew on the back side of the reel frame.  The Reed Switch Probe serial number and tape length are labeled on the sticker at the front of the reel flange. 

The Reed Switch Probe is featured with a shrouded stainless probe, LEDs, and a buzzer.  The probe is a normally open, simple reed switch that closes upon entering the magnetic field of the target anchor.  

A two-conductor tape serves to both lower the probe and connect the probe to the circuit board.  The switch closes upon entering magnetic field, the signal amplified, causing a beeping sound and LED flashing on the electronics readout on the reel. Anchor elevation is then read directly from the tape.

Problem: If the reed switch is not working, i.e. no buzzer sounds when the reed switch enters the magnet field of the target anchor, it is likely due to due to external causes like corrosion of the switch or twisted tape.

How to check:
Remove the  probe from the ground and visually check for damages like broken tapes, bent or twisted tape.  If this is the case, the wires inside the tape or the reed switch contact may be exposed to liquid and short-circuited so the switch will not work. 


1. The old tape will need to be repaired or replaced by a new tape.

2. Reset the reed switch beeping: 

- remove the battery

- press and hold the power button

- while still pressing the power button, re-insert the battery

- the beeping sound should be activated 

For more details, please refer to details manual of Reed Switch Probe